It is estimated that food allergies affect at least 12 million Americans, and the prevalence is rising. Food allergies cause roughly 30,000 emergency room visits and 100 to 200 deaths per year in the United States. Six (6) to 8 percent of children under the age of three have food allergies and nearly four percent of adults have them [National Institute of Allergy and Infectious Diseases (July 2004); “Food Allergy: An Overview” (PDF); National Institutes of Health. pp. 35]. The most common food allergies in adults are shellfish, peanuts, tree nuts, fish, and eggs, and the most common food allergies in children are milk, eggs, peanuts, and tree nuts [id.].
Cow's milk hypersensitivity is a common disease affecting 2.5% of infants in the first year of life in prospective studies [1], with approximately 60% of these milk disorders due to IgE-mediated mechanisms. Although the majority of children with IgE-mediated milk allergy develop tolerance by their teenage years [2], 15-20% have lifelong allergy. The mechanisms responsible for tolerance are still not clearly understood; it has been shown that the presence of IgE antibodies to distinct allergenic epitopes of cow's milk proteins can be used as a marker of persistent allergy [3]. Furthermore, a recent study demonstrated that the majority of milk allergic children can tolerate extensively heated forms of milk, and this subset of milk allergic patients are more likely to become tolerant to milk over time [4].
The current diagnostic modalities for food allergy include skin prick testing and measurement of serum specific IgE levels. These results give an indication of the likelihood of clinical reactivity, however, individual results do not provide prognostic information or distinguish between the different phenotypes of food allergy. The importance of sequential epitope recognition in the persistence of cow's milk allergy has been highlighted in several studies utilizing SPOTS membrane technology [5-7]. However, this method is time and labor intensive. Recently, peptide microarrays have been developed for large-scale epitope mapping using small quantities of serum. Shreffler et al. [8] used the peptide microarray immunoassay to examine serum samples from peanut allergic patients and confirmed that antigenic areas identified by this method correlated with areas defined by SPOTS membrane mapping. Furthermore, epitope recognition correlated with peanut allergy severity [8,9].
Similarly, peptide microarray results have been shown to correlate with clinical features of milk allergy. Milk allergic and tolerant patients demonstrated different epitope recognition patterns, with allergic patients having higher ratios of IgE to IgG4 binding than those tolerant to milk [10]. Decreases in IgE binding and increases in IgG4 binding to milk peptides were correlated with clinical improvement in children undergoing oral immunotherapy with milk [11]. Differences in epitope diversity appear to be associated with clinical features of food allergy. Studies of milk allergenic epitopes have further demonstrated that certain milk IgE epitopes may be used as candidate biomarkers to predict the development of tolerance to milk.
However, the use of IgE epitopes alone as biomarkers may not be sufficient to reliably predict whether an allergic individual will outgrow his or her allergy to milk. Moreover, characterization of allergenic epitopes can lead to a better understanding of the pathogenesis and tolerance induction of food allergy. Therefore, what is needed in the art are methods that provide greater specificity, reliability and efficiency for making such predictions and for characterizing allergenic epitopes. The present invention provides such methods.